Navigational instruments for ships

ABSTRACT

A navigational instrument for a ship incorporates an echo device arranged to measure the distance from a fixed part of the ship to the surface of the water at a point in advance of the ship. It includes a clinometer device arranged to measure the angle of fore and aft inclination of the ship from its static position and feed a corresponding signal to a computer together with the signal from the echo device. Indicating means receive the output from the computer which is in the form of an indication of the amount of the depression of the selected part of the ship and show such indication as a visual signal. The instrument may also incorporate a hog and sag clinometer providing a measure of any hog and sag present in the ship the output of said clinometer being also fed to the computer for correction of the output signal. The instrument may also incorporate means for feeding to the computer a signal which indicates the speed of the ship.

United States Patent i 1 91 Ferguson NAVIGATIONAL INSTRUMENTS FOR SHIPS[75] Inventor: Archibald McIntyre Ferguson, Cardross, Scotland [73]Assignee: The University Court of the University of Glasgow, Glasgovv,Scotland 221 Filed: Sept. 9, 1970 21 Appi. No.: 70,828

[30] Foreign Application Priority Data Sept. I6, 1969 Great Britain..45,475/69 52 US. Cl. .340/3, 340/1 R 51 I hit. c1 ..G01 s 9/66 [58]Field of Search ..'...340/-1 R, 3 R, 3 PR [56] References Cited UNITEDSTATES PATENTS 2,960,678 1 1/1960 Beard et al... ....-..'340/1 R2,083,344 6/l937 Newhouse et "1340/3 [4 1Ma'rch 20',' 1973 PrimaryExaminer-Ben iamin A. Borchelt Assistant Examiner-H. TudorAttorneyLarson, Taylor and Hinds 57 I ABSTRACT ,-A navigationalinstrument for a ship incorporates an echo device arranged to measurethe distance from a fixed part of the ship to the surface of the waterat a point in advance of the ship. It includes a clinometer devicearranged to measure the angle of fore and aft inclination of the shipfrom its static position and feed a corresponding signal to a computertogether with.

the signal from the echo device. Indicating means receive the outputfrom the computer which is in the form of an indication of the amount ofthe depression of the selected part of .the ship and show suchindication as a visual signal. The instrument may also incorporate a hogand sag clinometer providing ameasure of any hog; and sag present in theship the output of said clinometer being also fed to the computer forcorrection of the output signal The instrument may 'also incorporatemeans for feeding to the computer a signal which indicates the speed oftheship.

- 13 Claims, 3 Drawing Figures PATENTEDHARZOIHH SHEEI 1 or 2NAVIGATIONAL INSTRUMENTS FOR SHIPS have a loaded draught of 60 feet to70 feet many a channel which was once considered perfectly safe for allships provides a clearance between the bottom of such a large ship andthe bottom of the channel which calls for extra care in navigation. Thisdifficulty is aggravated by an effect which takes place when a ship ison the move in water the depth of which is not much greater than thedraught of the ship. This effect may be referred to as a Bernouillieffect. As a ship moves over the sea bottom in a shallow channel certainhydrodynamic forces come into play in the passage between the bottom ofthe ship and the sea bottom. More specifically the relative movement ofthe ship to the water in this passages causes a reduction in pressure inthe passage as the water is accelerated relatively to the ships bottomthrough the passage. The reduced pressure in the passage below the shipcauses the ship to be forced downwardly and thus to sink more deeply inthe water. This effect may be augmentedby the effect of the bulb-whichis a normal feature of the bow of a large cargo ship. The effect may befurther augmented by the thrust from the ships propellers. In aggregateit has been found by experiment that when a 200,000 ton ship is movingforward at the common service speed of about 14'knots in a comparativelyshallow waterway the bow may become depressed by as much as 8 feet. Thestern' is usually depressed also but customarily to a less extent. it isan object of the present invention to provide an instrument which willgive an indication on the bridge of the ship or at any other desiredposition of the amount of such depression and which can in fact bearranged to give a direct reading of the clearance between the lowestpart of the ship and the sea bed.

A navigational instrument according to the invention incorporates anecho device arranged to measure the distance from a fixed part of theship to the surface of the water at a point in advance of the ship andgenerate a corresponding signal, a clinometer device arranged to measurethe angle of fore and aft inclination of the ship from the staticposition i.e. its position when at rest and generate a correspondingsignal, computing means to receive the two signals and compute theamount by which at leastone selected part of the ship is depressed fromits static position and produce a corresponding computed output signalcorresponding with said amount and indicating. means arranged to receivethe computed signal and provide a visual indication of the amount of thedepression of the selected part of the ship.

v The computing means may bearranged to compute separately andsimultaneously the amounts by which the bow and the stern of the shipare depressed, the indicating means being arranged to provide separatevisual indications of the depressions of the bow and the stern.

The echo device may be arranged to project sound or electro-magneticwaves which are reflected from the surface of the water to be receivedas an echo by the device. Where an electromagnetic waveis employed itmay be in the radio frequency or optical frequency band. V

The echo device may include a boom arranged to project forwardly fromthe bow of the ship, the wave projector and receiver being mounted onthe tip of the boom. The wave projector may be a laser. in analternative construction the boom may support two light guides, e,g,bundles of optional fibers the outerends of which are downwardly turnedto face the surface of the water while the inner end of one is arrangedto receive the output of a laser, and the inner end of the other isdirected towards a light-sensitive device.

The clinometer device may incorporate two vertical cylindrical tubularcolumns arranged to contain a liquid, the columns being spaced in a foreand aft direction and being connected to a differentialpressure-sensitive device, the difference in the hydrostatic pressuresin the two columns providing an indication of the difference in liquidlevelsin the two columns and thus of the fore and aft inclination of theship.

The computing means may be arranged to provide an tom movable accordingto the computed signal received by the instrument against a scalecalibrated in appropriate units of draught, said scale being indepen-,dently manually movable so that it can be set to a datum position inwhich the pointer indicates the previously ascertained draught under theimmediate conditions of load while the ship is stationary. Theposition'of the pointer at any instant when the ship is under way willthen indicate the true draught of the ship at that instant.

The indicating device may also be fitted with a manually movable depthscale calibrated to the same scale as the scale of the draught, saiddepth scale being mounted on the movable scale of draught and beingitself independently movable relative to that scale in the samedirection. The use of this latter scale will be described later.

The or each pointer of the indicating means is preferably coupled to aone-way dashpot in such a way that the pointer is permitted to respondquickly to a rising signal, but is damped when responding to a reducingsignal. The indicating device thus tends to indicate maximum movement ofthe particular point on the. i

ships bottom. Also temporary effects such as those caused by waves donot cause large and rapid swings of the pointers and thereby providefalse readings or readings difficult to interpret.

The indicating means may be coupled to recording devices so that apermanent record is kept of the clearance between the bottom of the shipand the sea bed, at least during the period when the ship is in shallowwater.

In certain conditions of loading and/or sea swell a ship may deflect inhog or sag and this will have the effect of altering to some extent theamount of depression calculated for the stern. Normally the amount ofsuch hogging or sagging is small compared with the depression of the bowof the ship under way and therefore its effect can be disregarded. If itis desired that the amount of hogging and sagging should be taken intoaccount means to provide an indication of the amount of hogging orsagging can be provided to issue a correcting signal to the instrument.Such means may take the form of two clinometers attached to the? shipsstructure one forward and one aft of amidships, the difference in thereadings provided by the two clinometers when taken with the knowndimensions of the ship providing an indication of the amount by whichthe midship section has moved upwardly or downwardly in relation to thebow or the stem. The hog and sag signal is fed to the computing meanswhich latter corrects correspondingly the output signal.

In a large ship the water is distrubed in advance of the ship for someconsiderable distance often more than 40 feet. Preferably the boomshould be long enough to hold the echo device far enough in advance forthe signal directed to the surface of the water to meet undisturbedwater. Where this is not possible a correction for the amount of rise ofthe water surface in advance of the ship at the point where the signalreaches the surface may be made. This will vary according to the speedof the ship but such a correction may be applied to the indication givenby the instruments as a separate correction or the ships speed indicatormay be linked to the computing means so that the computing means willprovide the desired correction at each speed. The computing means willbe previously programmed to do this, the necessary information havingbeen obtained either in tank tests of a model of the ship or during fullscale trials.

A practical embodiment of the invention is illustrated in theaccompanying diagrammatic drawings in which FIG. 1 is a side elevationof the bow of a ship fitted with a wave projector mounted on the tip ofthe boom,

FIG. 2 is a side elevation of the bow of a ship fitted with light guidesin the form of bundles of optical fibers connected to a laser and alight-sensitive device respec' tively and FIG. 3 is a diagram showingthe working relationship of the various parts.

In the drawings, and referring particularly to FIG. 1, 1 denotes a bowportion of a ship fitted with a bulb 2. 3 denotes a clinometer devicearranged to measure the angle of fore and aft inclination of the shipand 1 generate a signal corresponding with the angle of inclination. 4denotes a boom projecting forwardly of the ship's bow and carrying atits outer end a directional electromagnetic wave transmitter or anacoustical wave transmitter 5 arranged to direct the transmitted wavedownwardly. The outer end of the boom 4 also carries a receiver 6 for anecho of the wave emanating from the transmitter 5. 7 denotes theposition of the water line when the ship is at rest, 8 denotes theposition of the water line when the ship is in motion and 9 denotes thebow wave caused by the forward motion of the ship. The dimension Xdenotes the artifi- Referring to FIG. 2, 11 and 12 denote bundles ofop-.

tical fibers havingtheirouter ends turned downwardly at 13 and 14respectively, the bundles of fibers 12 arranged to receive the output ofa laser or other light source constituting the wave transmittei" 5 andthe bundle of fibers 11 being directed towards a light-sensitive deviceconstituting the receiver 6.

In FIG. 3, l5 denotes a central computing means to which the receiver 6and the clinometer 3 are connected, the output of the computing meansbeing fed to a visual indicating device 16 having a pointer 17 arrangedto indicate details of the vertical position of the ships bow and apointer 18 arranged to indicate details of the vertical position of theships stern. 19 denotes manually movable depth scales. 21F and 21Adenote hog and sag clinometer devices located forward and aft of theamidships line 22 of the ship and arranged to provide to the computingmeans 15 details of the extent of hog or sag in the ship and 23 denotesan indicator of the speed of the ship also connected to the computingmeans, 15 to provide a signal thereto.

In practice, when the vessel is in sailing conditions of load and whileit is still at rest the manually operable scales 19 of draught on theindicating device 16 are adjusted until the actual draughts of thevessel 1 at the bow and at the stern are indicated opposite therespective pointers 17 and 18. Additionally in the indicating device theminimum depth of the water for a predetermined distance ahead asascertained from achart is indicated by moving the other manuallyoperable scales 20 so that the minimum ascertained water depth is alsoindicated opposite the pointers l7 and 18. The actual distance to thesea bed below the point on the ships bottom represented by each pointer17 and 18 may thus be read directly on the indicating device. When theship starts moving the Bernouilli effect already referred to between theships bottom and the sea bed causes the ship to move downwardly so thatthe draught increases, i.e. the original water level at rest asindicated at 7 rises towards the position indicated by 8, while a thrustresulting from the forward motion of the ship and operating on the hullstructure tends to cause the bow to become. further depressed and thisaction is frequently augmented by the propeller thrust. As the bowbecomes depressed under all these forces the echo device 5 moves nearerthe surface of the water and a signal indicating this change of heightis sent by the receiver 6 to the computing means 15. As the bow becomesdepressed the ship tilts forwardly slightly and the clinometer device 3detects the tilt and sends a tilting signal also back to the computingmeans 15 which latter operates to produce a computed output signal whichis a function of the true amount by which the bow has become depressed.The computing means also computes from the signals received the amountby which the stern has changed elevation and produces another outputsignal which is a function of such change of elevation. These signalsare sent to the indicating means 16 and the pointers l7 and 18 move overthe scales l9 and 20 amounts corresponding to the vertical movements ofthe bow and of the stern. The new figure for minimum distance to the seabed below the bow and below the stern can then be directly read off onthe scales 20. Where the echo device is not mounted far enough ahead ofthe bow to be beyond the bow effect the computing means takes account ofthe signal from the speed indicator 23 of the ship and operates to applythe previously ascertained correction so that the false reading at thebow is allowed for. The signals from the two. clinometer devices 21F and21A are sent to the computing means and a correction for hogging andsagging is also applied.

Many channels which were formerly regarded as too hazardous for largeships may be used safely by a ship fitted with the instrument of theinvention because the effective clearance below the ships bottom can beincreased to a safer figure by reducing the speed of the ship, theinstrument indicating when a safe speed is reached.

It will be noted that the depth at the stern is computed from the bowsignal. This is because the water at the stern when the ship is underway is too much disturbed to permit effective use of an echo device atthe stern.

A great advantage of the instrument of the device over an echo sounderis that the echo sounder informs of the conditions as they occur whereasthe instrument of the invention can provide an advance indication ofwhat will occur so that avoiding action can be taken if considerednecessary.

What is claimed is:

l. A navigational instrument for a ship incorporating an echo devicearranged to measure the distance from a fixed part of the ship to thesurface of the water at a point in advance of the ship and generate acorresponding signal, a clinometer device arranged to measure the angleof fore and aft inclination of the ship from its static position andgenerate a corresponding signal, computing means to receive the twosignals and compute the amount by which at least one selected part ofthe ship is depressed from its static position and produce acorresponding computed output signal corresponding with the said amountand indicating means arranged to receive the computed signal and providea visual indication of the amount of the depression of the selected partof the ship.

2. An instrument as claimed in claim 1 in which the computing means isarranged to compute separately and simultaneously the amounts by whichthe bow and the stern of the ship are depressed and the indicating meansis arranged to provide separate visual indications of the depressions ofthe bow and the stern.

3. An instrument as claimed in claim 1 in which the echo device isarranged to project sound waves.-

4. An instrument as claimed in claim 1 in which the echo device isarranged to project electro-magnetic waves.

I 5. An instrument as claimed in claim 1 including a boom arranged toproject forwardly from the bow of the ship, the echo device beingmounted on the tip of the boom.

6. An instrument as claimed in claim 4 in which a laser is provided togenerate the electro-magnetic wave 7.

is arranged to receive light issuing from the inner end of.

the other light guide.

8. An instrument as claimed in claim 1 in which the clinometer deviceincorporates two vertical cylindrical tubular columns arranged tocontain a liquid, the columns being spaced in a fore and aft directionand a differential pressure-sensitive device to which the colums areconnected.

9. An instrument as claimed in claim 1 in which the indicating meansincorporates a pointer for each selected point on the ships bottom atwhich a depth measurement is required, said pointer being movableaccording to the computed signal received by the instrument and at leastone scale against which said pointer is movable, said scale beingindependently manually movable and being calibrated in the appropriateunits.

10. An instrument as claimed in claim 9 in which each pointer of theindicating means is coupled to a one-way dashpot in such a way that thepointer is permitted to respond quickly to a rising signal, but is 13.An instrument as claimed in claim 1 in which the computing means isarranged to receive a signal indicative of the ships speed andmake acorrection in its own output signal in accordance with the amount bywhich the ships draughtis changed at the indicated speed.

s An instrument as claimed in claim 1 in which the

1. A navigational instrument for a ship incorporating an echo devicearranged to measure the distance from a fixed part of the ship to thesurface of the water at a point in advance of the ship and generate acorresponding signal, a clinometer device arranged to measure the angleof fore and aft inclination of the ship from its static position andgenerate a corresponding signal, computing means to receive the twosignals and compute the amount by which at least one selected part ofthe ship is depressed from its static position and produce acorresponding computed output signal corresponding with the said amountand indicating means arranged to receive the computed signal and providea visual indication of the amount of the depression of the selected partof the ship.
 2. An instrument as claimed in claim 1 in which thecomputing means is arranged to compute separately and simultaneously theamounts by which the bow and the stern of the ship are depressed and theindicating means is arranged to provide separate visual indications ofthe depressions of the bow and the stern.
 3. An instrument as claimed inclaim 1 in which the echo device is arranged to project sound waves. 4.An instrument as claimed in claim 1 in which the echo device is arrangedto project electro-magnetic waves.
 5. An instrument as claimed in claim1 including a boom arranged to project forwardly from the bow of theship, the echo device being mounted on the tip of the boom.
 6. Aninstrument as claimed in claim 4 in which a laser is provided togenerate the electro-magnetic waves.
 7. An instrument as claimed inclaim 1 in which the echo device includes a boom arranged to projectforwardly from the bow of the ship and two light guides are mounted onthe boom, the outer ends of the light guides being downwardly turned toface the surface of the water, a laser is arranged to direct its beaminto the inner end of one light guide and a light-sensitive device isarranged to receive light issuing from the inner end of the other lightguide.
 8. An instrument as claimed in claim 1 in which the clinometerdevice incorporates two vertical cylindrical tubular columns arranged tocontain a liquid, the columns being spaced in a fore and aft directionand a differential pressure-sensitive device to which the colums areconnected.
 9. An instrument as claimed in claim 1 in which theindicating means incorporates a pointer for each selected point on theship''s bottom at which a depth measurement is required, said pointerbeing movable according to the computed signal received by theinstrument and at least one scale against which said pointer is movable,said scale being independently manually movable and being calibrated inthe appropriate units.
 10. An instrument as claimed in claim 9 in whicheach pointer of the indicating means is coupled to a one-way dashpot insuch a way that the pointer is permitted to respond quickly to a risingsignal, but is damped when responding to a reducing signal.
 11. Aninstrument as claimed in claim 1 in which a recording device is coupledto the indicating means.
 12. An instrument as claimed in claim 1incorporating two hog and sag clinometer devices attached to the ship''sstructure one forward and one aft of amidships and arranged to provideoutput signals, the computing means being arranged to receive saidsignals and correct correspondingly its own output signal.
 13. Aninstrument as claimed in claim 1 in which the computing means isarranged to receive a signal indicative of the ships speed and make acorrection in its own output signal in accordance with the amount bywhich the ship''s draught is changed at the indicated speed.